(a) Field of the Invention
The present invention relates to a method of joining semiconductor substrates. More particularly, the present invention relates to a method of joining semiconductor substrates in which metal layers are formed.
(b) Description of the Related Art
In general, a metal layer and an insulating layer are deposited, or a micro pattern is formed, on one semiconductor substrate to form a semiconductor device. Further, the semiconductor device may also be formed by joining two or more semiconductor substrates on which a thin film layer, such as the metal layer and the insulating layer, and the micro pattern are formed.
A semiconductor substrate means a substrate obtained by growing a raw material of a semiconductor and single-crystallizing the raw material of the semiconductor like a rod, thinly die-cutting the singularly-crystallized raw material of the semiconductor according to crystal orientation, and grinding and polishing the die-cut semiconductor raw material, and is also referred to as a wafer.
When two or more semiconductor substrates are joined, an error generated during alignment of the semiconductor substrates must be considered, in general, in the alignment of semiconductor substrates, alignment keys formed in the semiconductor substrates are adjusted by using an optical measurement method to join the semiconductor substrates. However, in this case, a fine error may also be generated. Further, an alignment error by thermal expansion may be generated during a plurality of joining processes, or a metal layer may re-flow due to heat or pressure during the joining, so that a defect may be generated.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.